This invention relates to laser scribing system and method.
Besides photolithography, laser processing is well-known to process transparent conductive film which are used for liquid crystal device. YAG lasers have been used as laser beam sources in such a laser processing, the wave length being 1.06 microns for example. In such a laser processing, a groove is formed by continuously irradiation of a sequence of spot-shaped laser beams in the form of a line prescribed in a substrate to be processed. Because of this, the process condition, such as the energy density of a laser beam, the scanning speed, and so forth must be controlled in accordance with the characteristics of the transparent conductive film to be processed such as thermal conductivity. For this reason, it is difficult to improve the yield of product, when commercialized in mass-production, without compromising the specification of the product. Further, the laser energy, 1.23 eV per photon which corresponds to the wavelength of 1.06 microns, is very small as compared with 3 to 4 eV which represents an energy gap range of a usual transparent conductive film, such as tin oxide, indium oxide, indium tin oxide, zinc oxide, or the like. Still further, in a laser processing using Q-switching operation, laser beams have to scan at 30 to 60 cm/min with 0.5 to 1 W per spot of laser beam which has 50 microns in sectional diameter, 40 mm in focal distance, 3 KHz in pulse frequency and 60 namo seconds in pulse width. Due to such a high energy, cracking may cause on an underlying layer on which the transparent conductive layer has been formed and make the device defective. The damage of the underlying surface is caused in the shapes of scales.
In addition, with a prior art laser processing, a number of fine grooves can not be formed with 10 to 50 microns in interval, and etching must be implemented after laser processing because the imperfect formation of grooves. Further, the lasing condition must be monitored for each process to comply with the fluctuation of the output of the laser, especially the fluctuation at an initial output power. This invention is an improvement of Japanese Patent Application No.sho59-211,769.